Ethanol can be produced from grain-based feedstocks (e.g., corn, sorghum/milo, barley, wheat, soybeans, etc.), from sugar (e.g., sugar cane, sugar beets, etc.), or from biomass (e.g., lignocellulosic feedstocks, such as switchgrass, corn cobs and stover, wood, or other plant material).
In a conventional ethanol plant, corn is used as a feedstock and ethanol is produced from starch contained within the corn. Corn kernels are cleaned and milled to prepare starch-containing material for processing. Corn kernels can also be fractionated to separate the starch-containing material (e.g., endosperm) from other matter (such as fiber and germ). The starch-containing material is slurried with water and liquefied to facilitate saccharification, where the starch is converted into sugar (e.g., glucose), and fermentation, where the sugar is converted by an ethanologen (e.g., yeast) into ethanol. The fermentation product is beer, which comprises a liquid component, including ethanol, water, and soluble components, and a solids component, including unfermented particulate matter (among other things). The fermentation product is sent to a distillation system where the fermentation product is distilled and dehydrated into ethanol. The residual matter (e.g., whole stillage) comprises water, soluble components, oil, and unfermented solids (e.g., the solids component of the beer with substantially all ethanol removed, which can be dried into dried distillers grains (DDG) and sold, for example, as an animal feed product). Other co-products (e.g., syrup and oil contained in the syrup), can also be recovered from the whole stillage. Water removed from the fermentation product in distillation can be treated for re-use at the plant.
Various processes for recovering oil from a fermentation product are currently known in the art. Such processes, however, can be expensive, inefficient or even dangerous. For example, some process, such as that set forth in WO 2008/039859, utilize a solvent extraction technique that, in turn, requires the use of volatile organic compounds such as hexane. Other processes, such as that set forth in U.S. Application Publication No. 2007/0238891, utilize high amounts of heat. Still other conventional processes, such as that set forth in U.S. Application Publication No. 2006/0041152 and 2006/0041153, simply apply a centrifugal force to a fermented product in an attempt to separate an oil product.
Conventional processes for recovering oil from a fermentation product can sacrifice oil quality such that the oil contains a high level of free fatty acids. The presence of a high level of free fatty acids can hamper the production of end products such as, for example, the yield and quality of any bio-diesel eventually produced with the oil as a feedstock. Processes for producing ethanol, such as the process set forth in WO 2004/081193, produce fermentation byproducts which contain increased levels of oils while maintaining a low level of free fatty acids. However, upon application of a centrifugal force to the fermented product, an emulsion can form which effectively locks the valuable oil within the emulsion. Thus, a problem exists in that both conventional and novel processes, alike, cannot effectively, efficiently or safely separate or “break” quality oil from a fermented product.